# Licensed under a 3-clause BSD style license - see LICENSE.rst
import functools

import numpy as np

from ...tests.helper import pytest
from .. import Time
from ...utils.iers import iers  # used in testing

allclose_jd = functools.partial(np.allclose, rtol=1e-15, atol=0)
allclose_sec = functools.partial(np.allclose, rtol=1e-15, atol=1e-9)
# 1 nanosec atol

try:
    iers.IERS_A.open()  # check if IERS_A is available
except IOError:
    HAS_IERS_A = False
else:
    HAS_IERS_A = True


class TestTimeUT1():
    """Test Time.ut1 using IERS tables"""

    def test_utc_to_ut1(self):
        "Test conversion of UTC to UT1, making sure to include a leap second"""
        t = Time(['2012-06-30 12:00:00', '2012-06-30 23:59:59',
                  '2012-06-30 23:59:60', '2012-07-01 00:00:00',
                  '2012-07-01 12:00:00'], scale='utc')
        t_ut1_jd = t.ut1.jd
        t_comp = np.array([2456108.9999932079,
                           2456109.4999816339,
                           2456109.4999932083,
                           2456109.5000047823,
                           2456110.0000047833])
        assert allclose_jd(t_ut1_jd, t_comp)
        t_back = t.ut1.utc
        assert allclose_jd(t.jd, t_back.jd)

        tnow = Time.now()
        with pytest.raises(IndexError):
            tnow.ut1

    def test_ut1_to_utc(self):
        """Also test the reverse, around the leap second
        (round-trip test closes #2077)"""
        t = Time(['2012-06-30 12:00:00', '2012-06-30 23:59:59',
                  '2012-07-01 00:00:00', '2012-07-01 00:00:01',
                  '2012-07-01 12:00:00'], scale='ut1')
        t_utc_jd = t.utc.jd
        t_comp = np.array([2456109.0000010049,
                           2456109.4999836441,
                           2456109.4999952177,
                           2456109.5000067917,
                           2456109.9999952167])
        assert allclose_jd(t_utc_jd, t_comp)
        t_back = t.utc.ut1
        assert allclose_jd(t.jd, t_back.jd)

    def test_delta_ut1_utc(self):
        """Accessing delta_ut1_utc should try to get it from IERS
        (closes #1924 partially)"""
        t = Time('2012-06-30 12:00:00', scale='utc')
        assert not hasattr(t, '_delta_ut1_utc')
        # accessing delta_ut1_utc calculates it
        assert allclose_sec(t.delta_ut1_utc, -0.58682110003124965)
        # and keeps it around
        assert allclose_sec(t._delta_ut1_utc, -0.58682110003124965)


@pytest.mark.skipif('not HAS_IERS_A')
class TestTimeUT1_IERSA():
    def test_ut1_iers_A(self):
        tnow = Time.now()
        iers_a = iers.IERS_A.open()
        tnow.delta_ut1_utc, status = iers_a.ut1_utc(tnow, return_status=True)
        assert status == iers.FROM_IERS_A_PREDICTION
        tnow_ut1_jd = tnow.ut1.jd
        assert tnow_ut1_jd != tnow.jd